The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Current video data compression technologies include H.261, H.263, H.264, MPEG-2, and MPEG-4. According to the existing video compression technologies, encoding each image is carried out after dividing the same into fixedly sized macroblocks which are composed of rectangular 16×16 pixel areas of a luminance or luma component and rectangular 8×8 pixel areas of a chrominance or chroma component. All of the luma and chroma components of the respective macroblocks are spatially or temporally predicted, and the resultant predicted residuals undergo transform, quantization, entropy coding and the like before they are eventually compressed.
An encoding apparatus by the H.264/AVC compression standard subdivides each macroblock into blocks of smaller sizes 16×16, 8×8, and 4×4 to enter into an intra prediction encoding wherein 16×16 pixel blocks are processed in one of four prediction modes and 8×8 pixel blocks and 4×4 pixel blocks in one of nine prediction modes. As for an inter prediction encoding, each macroblock may be first divided into blocks of pixel sizes 16×16, 16×8, 8×16, 8×8, 8×4, 4×8, and 4×4. Transform is carried out in units of 8×8 or 4×4 pixel blocks, and quantization of transform coefficients utilizes a scalar quantization.
However, the inventor(s) has noted that 16×16 macroblock is deemed to be of an appropriate size for QCIF and CIF classes of small images, and would not be a size fit for high-resolution videos such as 4K×2K videos. In addition, the inventor(s) has noted that since typical video compression technologies utilize fixed size of macroblocks in encoding a video (although H.264/AVC prescribes subdividing and encoding macroblocks, the size of macroblocks is still fixed), an effective encoding of the high-resolution videos is yet to be achieved.
Further, the inventor(s) has noted that the operation in unison between encoding and decoding the video makes it difficult to expect a highly efficient video decoding from the already deteriorated compression efficiency of the high-resolution video encoding.
Therefore, to solve the above-mentioned problems, the present disclosure seeks to improve a video compression efficiency and a video reconstruction efficiency by extending a macroblock to various sizes, dividing an extended macroblock into subblocks of various sizes and shapes, and encoding/decoding a video by using different prediction units and transform units according to the sizes of the subblocks.